Mouse models have become increasingly important tools used to understand the origins and underlying causes of cancer. The completion of the mouse genome project has demonstrated that there is less than 1% difference in the genomes between mice and humans. As the mouse is a well-defined genetic model capable of high throughput phenotypic assessment, the ability to create novel mice through genetic engineering provides the opportunity for the development of unique cancer models. The purpose of the Animal Models Shared Resource is to provide the infrastructure necessary to generate and distribute genetically modified mice for cancer research to all participating MCCC investigators. Mayo Clinic Scottsdale has an outstanding track record in generating transgenic mice and will provide transgene services, while Mayo Clinic Rochester has generated a multitude of gene knockout mice and will provide the gene "knockout" services. Since 1999 14 MCCC members have utilized these resources representing 39% of the total services provided. The two mouse resources have been organized such that investigators have easy access to all services provided irrespective of the Mayo Clinic site from which they conduct their research.